Background and aims

Herbivore dung varies among species in terms of nutrients and microbial composition, but the effect of the microbial activity in the dung on plant growth and symbiotic association is largely unknown. This study aimed to investigate the influence of cow dung quantity and dung microbial activity on plant-microbe interactions (mycorrhiza, nodulation) and the growth of Trifolium pratense seedlings.

Methods

A mesocosm experiment was conducted with gradients of unsterilized or sterilized cow dung applied to pots with T. pratense seedlings. Biomass, relative growth rate (RGR), root phosphomonoesterase (PME) activity, nodulation, and root mycorrhizal colonization of the seedling were measured after 7 weeks.

Results

Growth of T. pratense increased with increasing dung supply, while sterilization marginally decreased growth by 15–20% (P = 0.068). Root nodulation increased with increasing dung supply but was significantly lower with sterilized dung. Both root PME activity and mycorrhizal colonization decreased with increasing dung supply but were unaffected by sterilization.

Conclusions

The decreased growth and nodulation due to dung sterilization aligned with our predictions but could not be attributed to reduced dung decomposition and nutrient availability. Instead, the reduced microbial activity from sterilization likely negatively impacted bacterial N₂-fixing activity and, consequently, plant growth. This suggests that herbivore dung’s effect on plant growth and interactions is more complex than previously anticipated, influenced not only by nutrient supply and stoichiometry but also by microbial composition and activity.

中文翻译：

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食草动物粪便中的微生物活性影响 Trifolium pratense 的结瘤和生长

 背景和目标

食草动物粪便在营养物质和微生物组成方面因物种而异，但粪便中的微生物活动对植物生长和共生关系的影响在很大程度上是未知的。本研究旨在探讨牛粪数量和粪便微生物活性对植物-微生物相互作用 （菌根、结瘤） 和 Trifolium pratense 幼苗生长的影响。

 方法

进行了一项中宇宙实验，将未绝育或绝育的牛粪梯度施用到装有 T. pratense 幼苗的花盆中。7 周后测量幼苗的生物量、相对生长速率 （RGR） 、根磷酸单酯酶 （PME） 活性、结瘤和根菌根定植。

 结果

T. pratense 的生长随着粪便供应的增加而增加，而绝育略微降低了 15-20% 的生长 （P = 0.068）。根瘤瘤随着粪便供应的增加而增加，但随着消毒粪便的增加，根瘤瘤显著降低。根 PME 活性和菌根定植均随着粪便供应的增加而降低，但不受灭菌的影响。

 结论

由于粪便消毒导致生长和结瘤减少与我们的预测一致，但不能归因于粪便分解和营养可用性减少。相反，灭菌引起的微生物活性降低可能会对细菌的 N₂ 固定活性产生负面影响，从而对植物生长产生负面影响。这表明食草动物粪便对植物生长和相互作用的影响比以前预期的要复杂，不仅受营养供应和化学计量的影响，还受微生物组成和活性的影响。